This is a fundamentally crucial book. David Graeber introduces different concepts such as money and debt. He takes a historical and anthropological way of explaining the origin. This breaks with the mainstream explanation, which is used in many Economics textbooks, saying that a barter economy existed before money arose.
There are some serious deficiencies in the economics curriculum in terms of what money is and how debt and money developed. By teaching that money was developed because pure barter in a more complex economy wasn't practical anymore, Mainstream economics has been using a misleading narrative and assumption for a long time. This had implications in the way credit, debt & money were modeled in macroeconomics models. Graeber claims that debt and credit historically appeared before money and barter. This has some serious implications for how currencies and markets developed and which role the state plays in this.
Also, have a look at this lecture by David Graeber to get a brief introduction to the book.